Small motors have been conventionally used for driving a lens of a digital camera and a video camera, and the like. It has been known to use a motor with a bearing which is movable in a thrust direction as well as a motor without a movable bearing.
A conventional motor 1 is shown in FIG. 2. Referring to FIG. 2, a stator 5 is disposed around a rotor 4 having a permanent magnet 3 which is fixed to a rotor shaft 2, and a bearing holder 7 is fixed to a metal case 6 of a stator 5 so as to be protruded on an outer side in an axial direction. A bearing 8 is movably held to the bearing holder 7. The bearing 8 supports one end of the rotor shaft 2 and is urged on a rotor shaft 2 side by an urging member 9 which abuts with an outer side face in the axial direction of the bearing 8 (see, for example, Japanese Patent Laid-Open No. 2002-191150).
Another conventional motor 11 is shown in FIG. 3. Referring to FIG. 3, a recessed part 14 is formed in a permanent magnet 13 fixed to a rotor shaft 12 and a radial bearing 15 for supporting an outer periphery of one end part of the rotor shaft 12 in a radial direction is accommodated in the recessed part 14. The rotor shaft 12 is urged by a flat spring 16 abutting with a shaft end of the rotor shaft 12 at a position of an axial center of the rotor shaft 12 on the output side of the rotor shaft 12 (see, for example, Japanese Patent Laid-Open No. 2004-140925).
There are, however, problems with the conventional motors discussed above. In particular, in conventional motor 1, since the bearing holder 7 is disposed to protrude on an outer side in the axial direction of the stator 5 and thus an overall length of the motor 1 becomes long and miniaturization of the motor 1 cannot be attained. Therefore, the bearing holder 7 becomes an obstacle when the motor 1 is mounted on an apparatus such as a camera and thus the motor 1 cannot be mounted on an apparatus that requires miniaturization.
Further, the size of the stator 5 occupying the overall length of the motor 1 becomes relatively small and thus an output torque in comparison with a dimension of the motor 1 becomes undesirably small.
Also, in the conventional motor 11, the shaft end of the rotor shaft 12 is directly pressurized by the flat spring 16 and a component force in a radial direction does not occur to the rotor shaft 12. Therefore, shaking in the radial direction of the rotor shaft 12 cannot be restrained and thus knocking noise occurs between the rotor shaft 12 and the radial bearing 15.